1. Field of the Invention
The present invention relates to oil and gas well drilling and more particularly, to an improved mud motor for drilling oil and gas wells and for drilling through obstructions, plugs and the like, in oil and gas wells wherein a high torque, low speed (i.e. low r.p.m.) motor is operated with a reciprocating valve and piston arrangement that uses differential fluid pressure for power and a transmission that isolates impact generated by the reciprocating valve and piston from the drill bit.
2. General Background of the Invention
In the drilling and maintenance of oil and gas wells, it is often required that a drill bit be used to eliminate an obstruction, plug, cement or like that is present within the well bore. In my prior U.S. Pat. No. 5,156,223, there is disclosed a drill that rotates for drilling through cement, rock, and any other media through which a drill bit must travel during oil and gas well drilling. In that prior patent, a reciprocating valve and piston arrangement is used to generate a high impact tool that drills and impacts the drill bit during the drilling process.
In prior U.S. Pat. No. 3,946,819, naming the applicant herein as patentee, there is disclosed a fluid operated well tool adapted to deliver downward jarring forces when the tool encounters obstructions. The tool of my prior U.S. Pat. No. 3,946,819, generally includes a housing with a tubular stem member telescopically received in the housing for relative reciprocal movement between a first terminal position and a second terminal position in response to fluid pressure in the housing. The lower portion of the housing is formed to define a downwardly facing hammer and the stem member includes an upwardly facing anvil which is positioned to be struck by the hammer. The tool includes a valve assembly that is responsive to predetermined movement of the stem member toward the second terminal position to relieve fluid pressure and permit the stem member to return to the first terminal position. When the valve assembly relieves fluid pressure, the hammer moves into abrupt striking contact with the anvil. The tool of prior U.S. Pat. No. 3,946,819, is effective in providing downward repetitive blows. The tool of the '819 patent will not produce upwardly directed blows.
In prior U.S. Pat. No. 4,462,471, naming the applicant herein as patentee, there is provided a bidirectional fluid operated jarring apparatus that produces jarring forces in either the upward or downward direction. The jarring apparatus was used to provide upward or downward impact forces as desired downhole without removing the tool from the well bore for modification. The device provides downward jarring forces when the tool is in compression, as when pipe weight is being applied downwardly on the tool, and produces strong upward forces when is in tension, as when the tool is being pulled upwardly.
In U.S. Pat. No. 4,462,471, there is disclosed a jarring or drilling mechanism that may be adapted to provide upward and downward blows. The mechanism of the '471 patent includes a housing having opposed axially spaced apart hammer surfaces slidingly mounted within the housing between the anvil surfaces. A spring is provided for urging the hammer upwardly. When it is desired to use the mechanism of the '471 patent for jarring, a valve including a closure and a compression spring is dropped down the string to the mechanism.
In general, the mechanism of the '471 patent operates by fluid pressure acting on the valve and hammer to urge the valve and hammer axially downwardly until the downward movement of the valve is stopped, preferably by the full compression of the valve spring. When the downward movement of the valve stops, the seal between the valve and the hammer is broken and the valve moves axially upwardly.
The direction jarring of the mechanism of the '471 patent is determined by the relationship between the fluid pressure and the strength of the spring that urges the hammer upwardly. Normally, the mechanism is adapted for upward jarring. When the valve opens, the hammer moves upwardly to strike the downwardly facing anvil surface of the housing.
In desirably low impact situations, there is a need for a drill motor that operates with well drilling fluid or drilling mud. Such "mud motors" have been commercially available for a number of years. All motors referred to as "mud motors" are of multi-lobe positive displacement operating on the "Moineau" principal. One of the limitations of these "mud motors" is their inability to operate in temperatures above about 250.degree. Fahrenheit. Another limitation of such "mud motors" is that they cannot operate for any length of time on nitrogen or nitrofied foam. They typically include a rotating member that is powered with the drilling mud as it flows through an elongated tool body. Suppliers of such "mud motors" include Drillex, Norton Christiansan, and Baker.
A second type of drill on the market is the "vane type". These drills were developed to overcome the temperature and gas operation limitations of the Moineau motors. The disadvantage of the vane type motors is their high speed and inability to tolerate foreign material.